concurrency

Description

Concurrency measures the number of events which have spans that overlap with the start of each event. Alternatively, this measurement represents the total number of events in progress at the time that each particular event started, including the event itself. This command does not measure the total number of events that a particular event overlapped with during its total span.

Syntax

concurrency duration=<field> [start=<field>] [output=<field>]

Required arguments

duration

Syntax: duration=<field>

Description: A field that represents a span of time. This field must be a numeric with the same units as the start field. For example, the duration field generated by the transaction command is in seconds (see Example 1), which can be used with the default of _time which is also in units of seconds.

Optional arguments

start

Syntax: start=<field>

Description: A field that represents the start time.

Default:_time

output

Syntax: output=<field>

Description: A field to write the resulting number of concurrent events.

Default: "concurrency"

Usage

An event X is concurrent with event Y if X.start is between Y.start and (Y.start + Y.duration)

If your events have a time that represents event completion and a span that represents the time before the completion, you need to subtract duration from the start time before the concurrency command:

Limits

There is a limitation on quantity of overlapping items. If the maximum tracked concurrency exceeds max_count, from the [concurrency] stanza in limits.conf, a warning will be produced in the UI / search output, and the values will be clamped, making them potentially inaccurate. This limit defaults to 10000000 or ten million.

Examples

Example 1

This example uses the sample dataset from the tutorial. Download the data set from this topic in the tutorial and follow the instructions to upload it to your Splunk deployment. Then, run this search using the time range, All time.

Use the duration or span of a transaction to count the number of other transactions that occurred at the same time.

This example groups events into transactions if they have the same values of JSESSIONID and clientip, defines an event as the beginning of the transaction if it contains the string "view" and the last event of the transaction if it contains the string "purchase".

The transactions are then piped into the concurrency command, which counts the number of events that occurred at the same time based on the timestamp and duration of the transaction.

The search also uses the eval command and the tostring() function to reformat the values of the duration field to a more readable format, HH:MM:SS.

Example 2

This example uses the sample dataset from the tutorial. Download the data set from this topic in the tutorial and follow the instructions to upload it to your Splunk deployment. Then, run this search using the time range, Other > Yesterday.

Use the time between each purchase to count the number of different purchases that occurred at the same time.

This example uses the delta command and the _time field to calculate the time between one purchase event (action=purchase) and the purchase event immediately preceding it. The search renames this change in time as timeDelta.

Some of the values of timeDelta are negative. Because the concurrency command does not work with negative values, the eval command is used to redefine timeDelta as its absolute value (abs(timeDelta)). This timeDelta is then used as the duration for calculating concurrent events.

Example 3

This example uses the sample dataset from the tutorial. Download the data set from this topic in the tutorial and follow the instructions to upload it to Splunk. Then, run this search using the time range, Other > Yesterday.

Use the time between each consecutive transaction to calculate the number of transactions that occurred at the same time.

This example groups events into transactions if they have the same values of JSESSIONID and clientip, defines an event as the beginning of the transaction if it contains the string "view" and the last event of the transaction if it contains the string "purchase".

The transactions are then piped into the delta command, which uses the _time field to calculate the time between one transaction and the transaction immediately preceding it. The search renames this change in time as timeDelta.

Some of the values of timeDelta are negative. Because the concurrency command does not work with negative values, the eval command is used to redefine timeDelta as its absolute value (abs(timeDelta)). This timeDelta is then used as the duration for calculating concurrent transactions.

Example 4

Determine the number of overlapping HTTP requests outstanding from browsers accessing splunkd at the time that each http request begins.

This relies on the fact that the timestamp of the logged message is the time that the request came in, and the 'spent' field is the number of milliseconds spent handling the request. As always, you must be an 'admin' user, or have altered your roles scheme in order to access the _internal index.

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